Because of the recognition that many hydrocarbon vapors are undesirable pollutants to the ambient atmosphere, the increased value of lost hydrocarbons because of the increased cost of the raw materials and labor associated with their obtention, and the fact that some of the hydrocarbons are suspected carcinogens, it has become technically and environmentally sound to develop processes for preventing loss of these hydrocarbons to the ambient atmosphere. One of the most recent technologies suggested for preventing the loss of vapors to the ambient atmosphere is the use of beds of micro- or macroporous ethylenically backboned polymers, most having a relatively high degree of crosslinking and either phenyl, modified phenyl, acrylic or modified acrylic moieties extending from the backbone, i.e. styrene divinylbenzene copolymers, polyacrylic or methacrylic polymers with or without styrene divinyl benzene and the like. These absorbent materials are stable under the absorption and desorbtion conditions and, in most instances, do not lose their absorbent characteristics on desorbtion as carbon so often does.
While these polymers and carbon both absorb hydrocarbon vapors and the polymers readily desorb most hydrocarbons, both are subject to static electrical charge build-up when warm or hot air is used as the sole desorbing media. The use of steam to desorb the beds results in a satisfactory desorbtion of the bed but introduces large quantities of condensate into the storage tank. Separate condensing and water separators are economically disadvantageous and result in loss of desorbed liquids. The use of mixtures of steam and air or inert gases result in losses of sorbed material because the input of air and steam into large tanks requires venting of the tank to the atmosphere, defeating the purpose of the recovery system.
Therefore, it is an object of the present invention to provide a process for sorbing and desorbing vapors of volatile hydrocarbons under conditions which are safe and efficacious.